In a radio signal communication system, information is transformed to radio signal for transmitting in form of an electromagnetic wave or radiation. These electromagnetic signals are further transmitted and/or received by suitable antennas.
Unidirectional antennas are used when there is a need to concentrate radiation in a desired direction. In some applications, such as office and household WiFi routers, the antenna is often placed off the room centre, e.g. beside a wall. In this case, unidirectional antennas with lateral radiation patterns are preferable to those with broadside radiation patterns. Large ground planes or cavities are needed in conventional lateral unidirectional antennas. It is desirable to reduce the size of the antenna so as to include the antenna in a more compact device and to reduce the visibility of the antenna.